The example at Callow in County Mayo is a rath, the term used for a ringfort constructed from earthen banks rather than stone, typically enclosing a circular area that once served as a defended farmstead during the early medieval period, roughly between the fifth and twelfth centuries. These were not military fortifications in any grand sense but rather the homesteads of farming families of some local standing, the enclosing bank and ditch serving to keep livestock in and wolves or opportunistic neighbours out.

Callow itself sits in the west of Mayo, a county whose bogland and drumlin country contain a considerable density of such monuments, many of them poorly recorded and only partially visible above ground after centuries of agricultural activity and turf cutting. The rath form, with its reliance on piled earth rather than dry-stone construction, is particularly vulnerable to erosion and the slow work of ploughing, which means that what survives at any given site can range from a well-preserved circular bank several metres high to little more than a faint rise in a field that only reveals itself in low raking light or from the air. Without more detailed recorded information available at present, the precise condition and dimensions of the Callow example remain unclear.